1. Field of the Invention
The present invention relates to a process for rejuvenation treatment of a photoresist development waste containing a photoresist and tetraalkylammonium ions and resulting from the process of producing electronic parts such as semiconductor devices, liquid crystal displays (LCD) and printed boards, and the like.
2. Related Art
In production of electronic parts such as semiconductor devices, liquid crystal displays and printed boards, and the like, a film of a negative or positive photoresist is formed on a substrate such as a wafer, then irradiated with a light or the like through a pattern mask, subsequently developed with a developer through dissolution therein of unnecessary part of the photoresist, and further subjected to etching or the like treatment, followed by removal of the insoluble photoresist film remaining on the substrate. Photoresists include positive photoresists which turn soluble where exposed to a light, and negative photoresists which turn insoluble where exposed to a light. The mainstream developer for the positive photoresists is an alkali developer. Although the mainstream developer for the negative photoresists is an organic solvent developer, an alkali developer is used for some negative photoresists.
An aqueous solution of a tetraalkylammonium hydroxide is usually used as an alkali developer as mentioned above. Thus, the dissolved photoresist and tetraalkylammonium ions are usually contained in a waste discharged from the process of development (called "photoresist development waste" or "photoresist alkali development waste"). Herein, although the counter ions of tetraalkylammonium ions are usually hydroxide ions (OH.sup.-) as is apparent from the foregoing, other ions may be some of the counter ions to form a salt(s) because such a waste (waste water), which differs from factory to factory, may be mixed with any foreign matter or may possibly be mixed with other waste water in some cases. Accordingly, the counter ions are not specified and the expression is instead made under the idea of "ions" in the generic description of the instant specification. Since tetraalkylammonium ions in the waste usually exist in the form of a tetraalkylammonium hydroxide as described above, however, the present invention will be described with priority given thereto.
Conventional methods of treating a photoresist development waste containing a photoresist and tetraalkylammonium ions include a method wherein all the waste is entrusted to a contractor for off-site disposal thereof, a method wherein the waste is concentrated by evaporation or reverse osmosis, followed by disposal (incineration or off-site disposal by contractor), and a method wherein the waste is subjected to a biodegradation treatment with activated sludge, and then discharged. Besides, in the case of a waste concentrated in the above-mentioned manner or a thick waste having a high tetraalkylammonium ion concentration from the beginning, there have been made attempts to concentrate, recover and reutilize tetraalkylammonium ions preferably in the hydroxide form by electrodialysis or electrolysis (naturally recovered in the hydroxide form by electrolysis).
The method comprising evaporation or reverse osmosis for concentration involves concentration of the alkali-soluble photoresist as well as tetraalkylammonium ions, with the result that the resulting liquid waste must inevitably be disposed of. The method comprising a biodegradation treatment with activated sludge is only capable of treating a low-concentration waste while requiring large-scale treatment facilities because the biodegradability of tetraalkylammonium ions is poor and proliferation of microorganisms capable of degrading other organic components, if mixed in the waste, becomes rather active while inactivating proliferation of microorganisms capable of degrading tetraalkylammonium ions to further deteriorate the biodegradability thereof. On the other hand, the method of recovering tetraalkylammonium ions preferably in the hydroxide form through concentration thereof by electrodialysis or electrolysis (naturally recovered in the hydroxide form by electrolysis), though best in aspects of a countermeasure against pollution, efficient utilization of resources, etc., involves a problem that a slight amount of impurities such as the photoresist and cations including Na.sup.+, K.sup.+ and Ca.sup.2+ (Na.sup.+ in particular) remains in the resulting recovered solution though a high purity of the solution is required for reutilization thereof as a photoresist alkali developer for use in production of, for example, electronic parts such as semiconductor devices, liquid crystal displays and printed boards.
Accordingly, an object of the present invention is to provide a simple and effective process for rejuvenation treatment of a photoresist development waste with elimination of the forgoing drawbacks of the conventional methods of treating a photoresist development waste containing a photoresist and tetraalkylammonium ions.